 UNLOCKING FEAR
Amygdala-enriched stathmin may hold the key to controlling fears, anxiety, say researchers
Fear is in your genes
WASHINGTON
In research that could lead to treatments for anxiety disorders, US scientists turned normally cautious mice into daredevils by switching off a gene that regulates fear. Led by Gleb Shumyatsky of Rutgers University, the researchers identified a gene in mice that controls their innate and learned senses of fear. The gene, called stathmin and found in high levels in the fear-managing amygdala section of the brain, controls a mouse's ability to react appropriately to impending danger.
The scientists demonstrated the gene's effect by effectively turning it off, after which the mice "became daredevils of a sort." "Mice without the gene show abnormally low levels of anxiety in situations that should instinctively inspire fear," the scientists said in their study published in the journal Cell.
While the discovery might suggest a future of bringing to life the fearless warriors of fantasy fiction, the scientists said it could eventually lead to more practical therapies in treating anxiety disorders.
"Little is known about the molecular mechanisms underlying fear reactions," said Shumyatsky. "We now have found that stathmin plays a critical role in both learned and innate fear."
The isolation of stathmin as key in regulating fear reactions came after scientists studied the behavior of mice that were conditioned to certain fear-provoking stimuli. By comparing the response of mice with and without stathmin to the stimuli--electric shocks and being left in unfamiliar open spaces--the scientists could measure the gene's importance in fear response.
"The findings provide genetic evidence that amygdala-enriched stathmin is required for the expression of innate fear and the formation of memory for learned fear," Shumyatsky said.
The mice in the test could be used as models for mental disorders involving anxiety states, according to Shumyatsky. "As a corollary, these animal models could be used to develop new antianxiety agents," he said.
Toxin's role in Alzheimer disease traced
SYDNEY
Researchers have discovered a toxin that plays an important role in the progression of Alzheimer disease, giving rise to hopes that drugs might be able to slow the onslaught of dementia. The toxin, called quinolinic acid, kills nerve cells in the brain and leads to brain dysfunction and ultimately death.
"Quinolinic acid may not be the cause of Alzheimer disease but it plays a key role in its progression," said researcher Karen Cullen from the University of Sydney. "It's the smoking gun, if you like. While we won't be able to prevent people from getting Alzheimer disease, we may eventually, with the use of drugs, be able to slow down the progression."
Researchers from St. Vincent's Hospital, Sydney and New South Wales universities, and Hokkaido University in Japan said drugs tested on stroke victims attack the pathway where the acid is made.
"There are several drugs that can block this pathway, which are already under investigation by our laboratory and others," said Gilles Guillemin of the Center for Immunology at St. Vincent's Hospital. The drugs would need to be tested for efficacy in Alzheimer.
A stinging discovery against pain
SYDNEY
More than one Australian animal can cause sudden death, but it was the painless passing of a young man stung by a marine snail 70 years ago that prompted a Melbourne academic to look to toxic mollusks for a cure for pain.
The 27-year-old died with his mother at his side after being stung by a cone-shell snail while on holiday on an island off the Great Barrier Reef in Queensland in 1935. Reading about the death in the Medical Journal of Australia decades later, Melbourne University associate professor Bruce Livett was struck by the painless nature of the man's death.
"There were very good descriptions of his death by his mother and the people around. He died a painless death, not at any stage did he feel any pain," Livett said.
The man slipped into unconsciousness shortly before his death but seemed to be at peace during the five to seven hours it took him to expire. "I thought, what is it that has dulled the pain? I went searching for the analgesic in the venom," Livett said.
A decade later, Livett and researchers at Melbourne University isolated what they hope is an analgesic drug in the conus victoriae, a species of marine cone snail found in western Australian waters.
Livett hopes that the drug, now undergoing trials, could be used to treat people with extreme pain from nerve damage (neuropathic pain) or from illnesses such as diabetes, cancer, and AIDS. "We are targeting it for neuropathic pain because that's where the largest need is," said Livett.
Appetite-suppressing hormone
WASHINGTON
American researchers have discovered a new hormone that suppresses appetite in laboratory rats, offering hope for the development of an antiobesity drug. Called obestatin, the hormone induced 20-percent weight loss in rats in one week, but researchers stressed it was too early to know if it would have similar effect in humans.
Obestatin's discovery follows that of the other three appetite-altering hormones--ghrelin, leptin, and melanocortin--which have not led to an efficient weight-losing treatment for 65 percent of Americans over the age of 20 who are overweight or obese.
Working with data from the Human Genome Project, researchers at the Stanford University School of Medicine also discovered that obestatin came from the same gene that made the appetite-boosting hormone ghrelin. These genetically related hormones with opposite effects could improve the understanding of the body's complex, appetite-regulating mechanism, said genetics professor Greg Barsh.
"This work is notable because it represents a completely new pathway," he said of the research that yielded obestatin.
The researchers stressed that the laboratory rats treated with obestatin that lost appetite and weight were not overweight animals at the start of the experiment, adding that the next step would be to administer the hormone to obese rats. Nevertheless, they said the new hormone had the potential to lead to a weight-loss treatment.
The research appears in Science.
Weight-loss drugs more effective with diet, exercise
WASHINGTON
Weight loss medication combined with a regimen of diet and exercise takes off twice as much weight as either treatment by itself, according to a study in the New England Journal of Medicine.
"Weight loss medications helped people lose weight, as did a program of lifestyle modification we designed to improve
eating and exercise habits," said lead researcher Thomas Wadden.
"However, we found that a combination of the two approaches produced approximately twice the weight loss of either intervention used alone," added the director of the Weight and Eating Disorders Program at the University of Pennsylvania School of Medicine.
The one-year study examined 180 women and 44 men with an average age of 44 years, weight of 106 kilograms, and body-mass index of 37.7 kg/m2, all randomly assigned to one of four treatment groups. The first group was prescribed weight-loss medication with little medical counseling; the second followed a regimen of diet and exercise; the third received a combination of the first two approaches; and the fourth received weight-loss medication with medical counseling on diet and exercise.
After one year, people in the third group following the combined treatment lost an average of 12.6 kilograms vis-à-vis an average of five kilograms for people in the first group who only took weight-loss medication. People in group two who dieted and exercised lost an average of 6.7 kilograms versus 7.5 kilograms for people in the fourth group.
Bye-bye tooth decay?
LISBON
Portuguese scientists said they had developed an experimental vaccine that has protected rats against tooth decay and could pave the way for a version that works on humans.
"What we found is that the animals vaccinated with this protein developed much smaller lesions than the control group that had not been vaccinated," said Paula Ferreira, one of three Oporto University researchers who worked on the vaccine. "There is still a long road to travel [for a human version]," she said in an interview with Lisbon-based TSF radio. Rats were used to test the experimental vaccine because the type of tooth decay they develop is similar to that which occurs in humans, she added.
Cup of coffee a day prevents hypertension
TOKYO
A Japanese medical research team has discovered drinking a cup of coffee or two a day could lower the risk of high blood pressure. The team led by a researcher at Keio University conducted the study on 4,554 men in their 20s to 70s who visited Tokyo clinics for check-ups on lifestyle-related disease from October 2003 to March 2004, the Tokyo Shimbun reported.
The study found that people who drank no coffee had the biggest ratio of high blood pressure, with the lowest risk of high blood pressure in the category drinking three cups or more, it said.
"Chlorogenic acid, a type of polyphenol contained in coffee, is considered to have the effect of expanding blood vessels," said the report. "But there also is a report that drinking coffee may lead to a cerebrovascular disorder for the elderly. Taking too much caffeine also induces excess stomach acid."
A rubber to stretch life?
PARIS, October
Scientists have synthesized a natural elastic that enables fleas to jump and cicadas to chirp, and believe the bouncy breakthrough may one day help people with chronic cardiovascular problems.
The polymer was made by Australian researchers, who took from Drosophila fruit flies a gene believed to give an insect protein called resilin its special elasticity. The gene was tucked into Escherichia coli intestinal bacteria, which were allowed to reproduce. The protein was then extracted and treated with light to make the final product--a substance so rubbery that it can be stretched to almost three times its original length without breaking.
The researchers, led by Christopher Elvin of CSIRO Livestock Industries, believe the recombinant resilin has innumerable applications, as it can be cast to shape and its flexibility and resilience are better than polybutadiene, one of the most widely manufactured commercial rubbers. They suggest that the synthetic elastin could be a future "biomedical" material that could replace defective tissues, such as natural elastin in the walls of arteries. Their study appears in Nature.
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